Move slice increments after completing header parsing

Slice increments are now done after completing header parse.
Earlier this was done before validating mmco related parameters
and calculating poc. In case there were errors that were detected
at this stage, slice increments were incorrect.

Bug: 199536974
Bug: 199733300
Bug: 205702093
Bug: oss-fuzz#38387
Bug: oss-fuzz#38482
Bug: oss-fuzz#40851
Test: ossfuzz generated poc in bug

Change-Id: I8569e9369e4ab6f6c69c81b937f111c299b7a134
(cherry picked from commit cd0385dc074c6ba119dffbcd3df669a9b9ca1790)
1 file changed